1. Field of the Invention
The present invention relates to an illumination device, an automotive lighting equipment which uses the illumination device, and a vehicle to which the automotive lighting equipment is mounted.
2. Description of Related Art
There have been known illumination devices in which light emitted from a semiconductor light emitting element such as a light emitting diode element or a semiconductor laser element is combined as excitation light with a fluorescent substance. Many light emitting diode elements and semiconductor laser elements that serve as an excitation light source use a nitride semiconductor that emits light in the ultraviolet to blue wavelength range. The fluorescent substance chosen to be combined with those excitation light sources is a material capable of converting light in the ultraviolet to blue wavelength range into green to red light through wavelength conversion. An illumination device that casts light of desired color is thus obtained. This type of illumination device is disclosed in, for example, WO 2002/091487.
Light emitted from a semiconductor light emitting element is harmful to the human body when the intensity of the light reaches a certain level. Laser light emitted from a semiconductor laser element, in particular, is coherent light which, upon entering the human eye directly, rises to an extremely high power density and hurts the eye.
The type of illumination device described above, even one having a semiconductor laser element as its light source, does not have the problem regarding the safety to the human eye because laser light scattered by a fluorescent substance is no longer coherent light. It has therefore been proposed to use a semiconductor laser element as a light source (excitation light source) in place of a light bulb or other conventional light sources.
For instance, JP 2008-73346 A proposes an electronic endoscopic device using a semiconductor laser as the light source of illumination light which illuminates an object inside a lumen. The electronic endoscopic device includes an endoscope insertion part and a device main body joined to the endoscope insertion part. In the device main body, a semiconductor laser element (laser chip) is installed as the light source. Laser light emitted from the semiconductor laser element is transmitted along a communication fiber laid in the endoscope insertion part, and irradiates a fluorescent filter (fluorescent member) provided at the tip of the endoscope insertion part. Irradiated with the laser light, the fluorescent filter emits white light to illuminate the object. An image pickup unit including an image sensor is also provided at the tip of the endoscope insertion part. The image pickup unit is driven by a signal processing part, which is provided in the device main body, and signal processing is performed on an image pickup signal from the image pickup unit, to thereby display an endoscopic image on a monitor.
With this type of electronic endoscopic device, there is a fear that damage to the device such as the breakage of the communication fiber may cause laser light to leak out of the endoscope insertion part. JP 2008-73346 A employs an illumination system that does not allow laser light to leak out of the endoscope insertion part in such situations. Specifically, the illumination system is structured to electrically sense the breakage or short circuit of a cable connecting the signal processing part and the image pickup unit and, upon detection of the breakage or short circuit of the cable, laser light output is controlled to prevent laser light from leaking out of the endoscope insertion part.
However, the illumination system described in JP 2008-73346 A is hardly applicable to other devices than endoscopic devices. Even if one manages to apply the illumination system to other uses, the application causes inconvenience by complicating the structure of the device to which the illumination system is applied. The inconvenience leads to a problem in that size reduction is difficult for the device to which the illumination system is applied when the device is not an endoscopic device and is intended for other uses such as general illumination.
When applied to general illumination or similar uses, the type of illumination device described above also has a fear that an accident such as the fluorescent substance (fluorescent member) falling off may cause emitted laser light to directly enter a person's eye. The safety of the illumination device to the human eye therefore drops in the event of such accidents.